Some mobile and/or wearable equipment for outdoor activity include orientation devices with AHRS sensors. Such equipment may often include cameras and/or vision devices, wherein the line of sight direction may be different from the velocity direction of the device.
There are known orientation devices that use magnetometers, corrected by Altitude Heading Reference System (AHRS) and Global Positioning System (GPS) data used as input for a Kalman filter, in order to find the motion direction relative to the true north. Such systems are usually inherently inaccurate and affected by metals and magnetic disturbances.
Other, more accurate inertial sensor systems are usually very expensive, heavy and too large for outdoor activity user equipment.